add import library (.dll.a) file type for Cygwin

- needed to link std correctly

Signed-off-by: Ookiineko <chiisaineko@protonmail.com>

Author: Ookiineko

src/cargo/core/compiler/build_context/target_info.rs

@@ -438,7 +438,8 @@ impl TargetInfo {
                 });
             } else if suffix == ".dll"
                 && (target_triple.ends_with("windows-gnu")
-                    || target_triple.ends_with("windows-gnullvm"))
+                    || target_triple.ends_with("windows-gnullvm")
+                    || target_triple.ends_with("cygwin"))
             {
                 // See https://cygwin.com/cygwin-ug-net/dll.html for more
                 // information about GNU import libraries.